In various fields of art and technology there is need to remove or react a material in selected and selective areas. Such selective action is used in etching in the production of decorative patterns, in the formation of information patterns and in industrial production and in diverse uses and applications. In one application of the formation of information patterns in industrial production a so-called high technology use and application in semiconductor manufacture has put a severe strain on the ability to form these patterns rapidly, effectively, to result in practical and useful procedures for creating particularly high quality fine resolution patterns of material. In micro-electronics industries such as the production of semiconductors it is usual to form a pattern of a desired electronic circuit or desired semiconductor element on a surface and selectively remove material to form a resist layer whose fineness of definition is in the order of the wave length of light or substantially finer than the wave length of light.
One such procedure is known in the art as microlithography, terminology derived from classical lithography which it resembles. In this procedure as now practiced, a layer of material such as a chalcogenide on a suitable substrate is treated photographically with a pattern of activating radiation to form a selectively etchable chalcogenide which, when etched, is employed as a lithographic mask or resist for semiconductor element production. One photo-activating mechanism in such procedures is known in the art as photodoping or silver-doping in which a silver image is driven into the chalcogenide surface and acts to "cap" or protect the silver-containing areas against etching. According to Yoshikawa U.S. Pat. No. 4,127,414 a pattern of silver is driven into the chalcogenide surface by a pattern of driving radiation; according to Masters et al. U.S. Pat. No. 4,269,935 a pattern of silver is formed on the chalcogenide surface by photographic exposure and processing of a silver halide deposit and this silver pattern is driven into the chalcogenide by flooding with driving radiation. In either way, a silver protective cap is formed, protecting the chalcogenide against the etch to produce a negative resist. For the resist formation the chalcogenide can be etched with an aqueous alkali or other solution to dissolve the unprotected chalcogenide on the substrate; freon plasma etching has also been used.
Various improvements in such systems are desirable. First, it is desirable to produce photographically positive rather than photographically negative images or relief layers in which the areas removed from the chalcogenide resist are those which are exposed to radiation rather than those which are unexposed. Also, greater uniformity of etched lines is desired so that increased fineness of resolution can be achieved. Further, in semiconductor manufacture and in virtually all other photo-exposure systems it is desired to generate systems having greater light or radiation sensitivity, and efforts to improve photographic speed in virtually all light or radiation-responsive systems have been going on for many, many decades.